kernel/linux.git/arch/um/os-Linux, branch v6.12.80

um: Fix FD copy size in os_rcv_fd_msg()

2025-09-25T09:13:42+00:00

[ Upstream commit df447a3b4a4b961c9979b4b3ffb74317394b9b40 ] When copying FDs, the copy size should not include the control message header (cmsghdr). Fix it. Fixes: 5cde6096a4dd ("um: generalize os_rcv_fd") Signed-off-by: Tiwei Bie Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin

um: remove copy_from_kernel_nofault_allowed

2025-04-10T12:39:25+00:00

[ Upstream commit 84a6fc378471fbeaf48f8604566a5a33a3d63c18 ] There is no need to override the default version of this function anymore as UML now has proper _nofault memory access functions. Doing this also fixes the fact that the implementation was incorrect as using mincore() will incorrectly flag pages as inaccessible if they were swapped out by the host. Fixes: f75b1b1bedfb ("um: Implement probe_kernel_read()") Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20250210160926.420133-3-benjamin@sipsolutions.net Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin

um: Remove unused mm_fd field from mm_id

2024-09-12T18:36:22+00:00

It's no longer used since the removal of the SKAS3/4 support. Signed-off-by: Tiwei Bie Signed-off-by: Richard Weinberger

um: remove variable stack array in os_rcv_fd_msg()

2024-09-12T17:51:26+00:00

When generalizing this, I was in the mindset of this being "userspace" code, but even there we should not use variable arrays as the kernel is moving away from allowing that. Simply reserve (but not use) enough space for the maximum two descriptors we might need now, and return an error if attempting to receive more than that. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202407041459.3SYg4TEi-lkp@intel.com/ Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger

um: refactor TLB update handling

2024-07-03T15:09:50+00:00

Conceptually, we want the memory mappings to always be up to date and represent whatever is in the TLB. To ensure that, we need to sync them over in the userspace case and for the kernel we need to process the mappings. The kernel will call flush_tlb_* if page table entries that were valid before become invalid. Unfortunately, this is not the case if entries are added. As such, change both flush_tlb_* and set_ptes to track the memory range that has to be synchronized. For the kernel, we need to execute a flush_tlb_kern_* immediately but we can wait for the first page fault in case of set_ptes. For userspace in contrast we only store that a range of memory needs to be synced and do so whenever we switch to that process. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240703134536.1161108-13-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: simplify and consolidate TLB updates

2024-07-03T15:09:50+00:00

The HVC update was mostly used to compress consecutive calls into one. This is mostly relevant for userspace where it is already handled by the syscall stub code. Simplify the whole logic and consolidate it for both kernel and userspace. This does remove the sequential syscall compression for the kernel, however that shouldn't be the main factor in most runs. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240703134536.1161108-12-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: Delay flushing syscalls until the thread is restarted

2024-07-03T15:09:49+00:00

As running the syscalls is expensive due to context switches, we should do so as late as possible in case more syscalls need to be queued later on. This will also benefit a later move to a SECCOMP enabled userspace as in that case the need for extra context switches is removed entirely. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240703134536.1161108-9-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: remove copy_context_skas0

2024-07-03T15:09:49+00:00

The kernel flushes the memory ranges anyway for CoW and does not assume that the userspace process has anything set up already. So, start with a fresh process for the new mm context. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240703134536.1161108-8-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: remove LDT support

2024-07-03T15:09:49+00:00

The current LDT code has a few issues that mean it should be redone in a different way once we always start with a fresh MM even when cloning. In a new and better world, the kernel would just ensure its own LDT is clear at startup. At that point, all that is needed is a simple function to populate the LDT from another MM in arch_dup_mmap combined with some tracking of the installed LDT entries for each MM. Note that the old implementation was even incorrect with regard to reading, as it copied out the LDT entries in the internal format rather than converting them to the userspace structure. Removal should be fine as the LDT is not used for thread-local storage anymore. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240703134536.1161108-7-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: compress memory related stub syscalls while adding them

2024-07-03T15:09:49+00:00

To keep the number of syscalls that the stub has to do lower, compress two consecutive syscalls of the same type if the second is just a continuation of the first. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240703134536.1161108-6-benjamin@sipsolutions.net Signed-off-by: Johannes Berg